Preform roller

ABSTRACT

A METHOD AND APPARATUS FOR MANUFACTURING AN IMPROVED FIBER PREFORM WHICH MAY BE USED IN THE SUBSEQUENT BAG MOLDING OF FIBER REINFORCED PLASTIC ARTICLES SUCH AS TANKS OR THE LIKE. THE METHOD COMPRISES THE STEPS OF RANDOMLY DEPOSITING SHORT REINFORCING FIBER ON A FORM, BINDING THE FIBERS TOGETHER WITH A SETTABLE RESIN BINDER, AND ROLLING THE RESIN COATED FIBERS ON THE FORM INTO A DIMENSIONALLY NIFORM POROUS MAT. THE APPARATUS INCLUDES A ROTATABLE LAY-UP FORM, MEANS FOR RANDOMLY DEPOSITING THE REINFORCING FIBERS IN A POROUS LAYER ON THE FORM, MEANS TO COAT THE FIBERS WITH A SETTABLE RESIN BINDER, AND MEANS TO PROGRESSIVELY PRESS THE FIBERS ALONG THE LENGTH OF THE FORM INTO A UNIFORM WALL THICKNESS.

July 4, 1972 A. J. WILTSHIRE PREFORM ROLLER Filed June 5, 1970 90 an, 00EM 00 0 m 7x M41, V @W JJM Z w ew A; 5 p

United States Patent O 3,674,599 PREFORM ROLLER Arthur J. Wiltshire,Cleveland, Ohio, assignor to Structural Fibers, Inc., Chardon, OhioFiled June 5, 1970, Ser. No. 43,736 Int. Cl. B32b 31/20 U.S. Cl. 4258011 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus formanufacturing an improved fiber preform which may be used in thesubsequent bag molding of fiber reinforced plastic articles such astanks or the like. The method comprises the steps of randomly depositingshort reinforcing fibers on a form, binding the fibers together with asettable resin binder, and rolling the resin coated fibers on the forminto a dimensionally uniform porous mat. The apparatus includes arotatable lay-up form, means for randomly depositing the reinforcingfibers in a porous layer on the form, means to coat the fibers with asettable resin binder, and means to progressively press the fibers alongthe length of the form into a uniform wall thickness.

BACKGROUND OF THE INVENTION A fiber preform is an article having thegeneral shape of an article to be subsequently molded and consists of aporous wall formed by a multitude of randomly oriented short lengths offibers which are bonded together by a settable resin. Fiber preforms areused in the manufacture of hollow articles such as tanks by positioningthem in a mold, compressing them internally by inflating a bag therein,and then impregnating them with a thermosetting resin. Earlier methodsof preform use are described in U.S. Letters Patent to Wiltshire3,138,507, and Geringer 3,137,898. Under these earlier methods, thepreform was a composite of one or two end preforms and a cylindricallyrolled blanket side wall. One of the deficiencies of this compositemethod is the overlapping joint structure where an end preform abuts thecylindrically rolled blanket or where the ends of the blanketlongitudinally abut each other. Overlapping may create an irregularityin the amount of reinforcing material at a joint and may not provideuniform interlocking of the reinforcing fibers at the joint. It is,therefore, a desired molding practice to minimize the number of jointsin the preforms and maintain uniformity in wall thickness throughout thepreform.

An improved preform with a machine and method for making the same isdisclosed in my copending joint U.S. patent application Fiber Preformand Method and Apparatus for Making Same, Ser. No. 742,692, filed July5, 1968. According to the teachings of the application, a preform may beproduced by depositing or laying up short reinforcing fibers on a formhaving a cylindrical portion and an end portion while spraying a resinbinder thereon which, when subsequently cured, produces a rigid porouspreform. Each preform produced according to that invention may becombined with a similar preform within a mold so that a molded articlemay be formed which has only one preform joint.

In producing fiber preforms in accordance with the teachings of theaforementioned application, it is important that those preforms satisfyrigid dimensional requirements. In particular, the exterior dimensionsof the preform must be substantially equal to the interior dimensions ofthe mold to be used and lie within a narrow tolerance range.

If the preform is oversized, it cannot be inserted into 3,674,599Patented July 4, 1972 the mold and must be discarded. There is noeconomical way to reshape the preform after the binding resin has set,nor is there a method of salvaging the materials forming the preform.Consequently, valuable products, time, and materials are lost.

SUMMARY OF THE INVENTION The present invention represents an improvementin the method and apparatus of my joint invention disclosed in theaforementioned copending application Ser. No. 742,692. The improvementcomprises, basically, rolling or pressing the fiber preform with aroller before it is removed from the lay-up form on which it isdeposited and before the binder resin has set to any significant degree.This rolling action produces a fiber preform having a dimensionallyuniform outside diameter so that the preform may be readily insertedinto the mold.

As described in my copending joint application, short reinforcing fibersare randomly deposited on a rotating form and are simultaneously sprayedwitha resin binder to form the porous walls of a preform. The wallthickness is generally controlled by the volume of fibers depositedalong the length of the form. In the embodiment shown therein, the fibervolume is regulated by the transport rate of a carriage conveying asource of fibers and the rate at which the source produces fibers. Withthe apparatus disclosed in my copending joint application, fibers aredirected from the source to the lay-up form under the influence of thepropelling force of the fiber source and a vacuum applied internally tothe form. As a precaution to insure wall uniformity, the source of fibercomprises two filament choppers, one leading the other as the carriagetraverses the form. This duplication is intended to even out the randomnature of the fiber deposition.

To further improve the uniformity of wall thickness, the presentinvention provides a roller in rolling contact with the fibers depositedon the rotating form. In the preferred embodiment the roller isrelatively short in comparison to the length of the lay-up form and itis mounted on the carriage for movement therewith. The roller closelyfollows the zone at which fibers are deposited and sprayed so that theymay be rolled before the resin binder has set.

This method of pressing or rolling the preform as it is being formedresults in a more uniform or dimensionally accurate wall thickness whichin turn permits the manufacture of quality fiber reinforced articles. Bymaintaining accurate wall thickness the preform may be dimensioned tofit with minimal clearance between its outer surface and the innersurface of a mold. The accurately rolled preform may be uniformlycompressed within the mold and impregnated with resin without producingharmful resin rich areas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspectiveview of a machine incorporating this invention.

FIG. 2 is a perspective view, on an enlarged scale, of the preformroller of this invention.

FIG. 3 is a side elevational view showing the rolling surface of thepreform roller.

FIG. 4 shows an end elevational view of the mounting arrangementprovided for the preform roller.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the presentinvention, FIG. 1 shows a machine 10 having as its principal parts aframe or housing 11, a lay-up form 12, a suction blower or fan 13, and acarriage 14. On the carriage 14 is mounted a source of fibers comprisinga pair of conventional filament cutters or choppers 16 and 17, acorresponding pair of binder spray nozzles 18 and 19, and a preformroller 20. A more 3 detailed description of other parts of the machinemay be found in my copending joint patent application, Ser. No. 742,692,mentioned above.

The lay-up form 12 is an elongated cylindrical member suitably journaledin bearings (not shown) mounted on the frame '11 and suitably drivenabout a horizontal longitudinal axis 21 by a motor (also not shown). Theform 12 is hollow and is provided with a multitude of perforations orholes 22 in its exterior surface. The hollow interior of the form 1 2 isconnected to the vacuum fan 13 to thereby draw air through theperforations 22 into the interior of the form 12.

The carriage 14 translates along a path above the form 12 and parallelto the longitudinal axis 21 of the form. A set of rollers or wheels 24support the carriage 14 on a guide rail '25 mounted on the frame 11above the form 12. The two choppers 16 and 17 are mounted on the lowerside of the carriage 14 and are spaced apart along the longitudinaldirection of the form 12. The choppers 16 and 17, rotatably driven by acommon motor 26 and separate clutches (not shown), operate to cut orchop continuous filaments of glass fiber or other reinforcing fibersinto short lengths and direct these cut pieces downwardly against theform 12 as illustrated at zones 27 and 28. The fibers are randomlydeposited on the form 12 and held in position by the suction applied tothe perforations 22 by the fan 13.

An arm 29 depending from the carriage 14 supports the spray nozzles '18and 19 adjacent the areas or zones 27 and 2-8 at which chopped fibersare being deposited. The spray nozzles 18 and 19 are adapted to spraysettable resin binder in the areas in which the cutters 16 and 17,respectively, deposit cut fibers. The lay-up form 12 is provided with acylindrical sidewall portion 32 and an end portion 33. Fibers aredeposited and sprayed along the length of the cylindrical portion 32 andover the end portion 33 of the form. The portions 32 and 33 have thesame general configuration as a portion of the eventual article intowhich the preform will be molded.

As viewed in FIG. 1, the carriage -14 traverses along its path fromright to left. Suitable control circuitry is provided to first operatethe leftward cutter 16 and spray nozzle 18. After sufiicient fibers havebeen deposited and sprayed in a layer on the form 12 at the beginning orrightward end of a sidewall portion 31 of a fiber preform, carriagemovement may be initiated. Upon movement of the carriage 14 to the left,the rightward chopper 17 and spray nozzle 19 are operated to add asecond course or layer of resin coated fibers to the sidewall portion31. This double application of resin coated fibers insures that theresulting fiber mat wall will be relatively uniform in thickness. Thefibers are deposited and sprayed in such a manner as to leave suflicientvoids between individual fibers to form a porous and somewhatcompressible mat which may be subsequently impregnated with athermosetting resin during the molding operation.

To improve the uniformity of wall thickness and density of the preform,the present invention provides the preform roller 20 to roll or pressthe sidewall extent of the fiber preform while it is on the form 12. Inthe preferred embodiment the preform roller 20 is mounted on the carnage14 slightly behind or rearward of the zones or areas 27 and 28 wherefibers are being deposited and sprayed with resin binder. It may beseen, of course, that the roller 20 will closely follow these areas 27and 28 as the carriage 14 traverses the form 12.

The preform roller 20 is rotatably mounted on a shaft 36 which in turnis secured in a yoke 37 with a pair of set screws 38. The yoke 37 ispositioned on a channel or arm 39 with a pair of screws 40. The arm 39is mounted on a hinge 41 which is secured to a lower surface 42 of thecarriage 14. The hinge 41 and the arm 39 are adapted to permit theroller 20 to engage the preform sidewall portion 31 when the arm 39 isapproximately 45 from the horizontal. The roller 20 is permitted by itshinge mounting to move radially towards or away from the longitudinalaxis 21 of the form 12 to accommodate variations in the diameter ofvarious forms employed on the machine 10.

As may be seen, the pivot or axis 46 of the hinge 41 is mounted parallelto the longitudinal axis 21 of the form 12 so that the arm 39 moves inplanes perpendicular to the longitudinal axis 21. Similarly, the rollershaft 36 is arranged parallel to the longitudinal axis 21 of the form sothat the roller 20 is easily rotated by frictional contact with thesidewall portion 31 as the form 12 rotates. In some instances it may bedesirable to skew the preform roller 20 slightly relative to thelongitudinal axis 21 of the form to bring its axis perpendicular to alead angle determined by the relative rotational speed of the form 12and the transport speed of the carriage 14, but in most instances thishas been found unnecessary. This can be effectively done by elongatingone of the holes in the arm 39 associated with one of the screws 40attaching the yoke 37 to the arm 39.

A bevel 48 is provided on the left end or face of the roller 20 to guidestray fibers under its rolling surface 49. Normally, the roller 20engages the sidewall portion 31 only as the carriage 14 moves to theleft as shown in FIG. 1. It is not necessary to roll the fibers whichcover the end portion 33 of the form 12 since they will conform to theinterior of a mold in which the preform will be positioned. On therightward return of the carriage 14, the preform roller 20 may bemanually retracted upward and the channel or arm 39 may be locked in anupward position, as shown in FIG. 4, by a latch '51. To adjust thecontact pressure of the roller 20 on the sidewall portion 31, a suitablenumber of washers or weights 52 may be positioned on a pin 53 welded tothe yoke 37.

Since the preform roller 20 moves with the source of fibers and thesource of resin binder, the fiber mat may be rolled before the bindersets and the fiber mat becomes rigid. Because the roller 20 floatsradially with respect to the axis 21 of the form 12 and because of itsrelatively short length in relation to the length of the form 12, theroller adjusts for any eccentricity or other misalignment of the form 12relative to the frame 11 or carriage guide rail 25. As mentioned, theroller is effective to flatten stray fibers and tends to level outrandom variations in the thickness of the fiber mat. Thus a preform maybe manufactured to relatively close tolerances. The nominal dimensionsof the preform may accordingly be chosen close to the interiordimensions of a mold in which it will be subsequently processed withoutcausing problems of interference during insertion into the mold.Further, the density of the sidewall portion of the preform may beregulated by choosing the proper contact pressure, without destroyingthe porosity of the fiber mat. After the fiber mat has been rolled itmay be cured in an oven and then removed from the form 12.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondisclosed and claimed herein.

What is claimed is:

1. An apparatus for making preforms for fiber reinforced articlescomprising a frame, a form journaled for rotation on said frame, meansfor randomly depositing fibers on said form to create a porous fiberpreform thereon, means to coat said fibers with a settable resin binder,and means disposed relative to said coating means to progressively presssaid fiber preform along the length of said form after said coatingmeans has coated said fibers without destroying the porosity of saidpreform.

2. An apparatus as set forth in claim 1 wherein said pressing means is aroller having its axis of rotation generally parallel to the axis ofrotation of said form.

3. An apparatus as set forth in claim '2 wherein said roller issubstantially shorter in length than the length of said form.

4. An apparatus as set forth in claim 3 wherein said form is anelongated member and a carriage is provided to transport said roller ina. direction parallel to the longitudinal axis of said form, wherebysaid roller progressively presses said fiber preform along its length.

5. An apparatus as set forth in claim 4 wherein said roller is providedwith a beveled edge at an end facing the direction of transport.

6. An apparatus as set forth in claim 4 wherein said depositing meansincludes a source of fibers mounted, with said coating means, on saidcarriage.

7. An apparatus as set forth in claim 2 wherein said roller is radiallymovable relative to said axis of said form.

8. An apparatus as set forth in claim 7 wherein means are provided toadjust the contact pressure between said roller and said fiber preform.

9. In a machine for manufacturing preforms for fiber reinforced plasticarticles, the machine having a frame, an elongated form journaled forrotation about its longitudinal axis on said frame, said form providinga perforated surface with a general configuration of the eventualarticles, a blower connected to apply a suction to the perforations insaid surface, a source of short fibers for randomly depositing a porouslayer of fibers on said perforated surface, means to coat said fiberswith a settable resin without filling the voids therebetween, and acarriage, cooperating with guide means on said frame, for transportingsaid source of fibers along a path parallel to said longitudinal axis,the improvement which comprises a roller, mounted on said carriage formovement with said fiber source, for pressing said fiber layer into adimensionally uniform wall.

10. A machine as set forth in claim 9 wherein said coating means is aspray nozzle mounted on said carriage and said roller is arranged onsaid carriage to follow a spray zone of said nozzle as said carriagetransports said spray nozzle along said path.

11. Apparatus for making closed end cylindrical preforms for fiberreinforced articles comprising a frame, an elongated cylindrical formsupported at one end in cantilever fashion for rotation about itslongitudinal axis on said frame, a surface defining the exterior of saidform including a multitude of perforations therein, a blower connectedto apply suction to the perforations in said surface, means for randomlydepositing fibers on said form to create a porous fiber preform thereon,means to coat said fibers with a settable resin binder, a carriagemovable on said frame parallel to the axis of said form, a roller havinga length substantially shorter than the length of said form for pressingsaid fibers into a dimensionally uniform wall, said roller being mountedon said carriage for axial movement therewith, means biasing said rollertowards the axis of said form, and mounting means permitting said rollerto move radially with respect to the axis of the form whereby saidroller adjusts to misalignment of the form relative to the frame.

References Cited UNITED STATES PATENTS 2,990,004 6/1961 Sowers et al156-377 3,170,197 2/1965 Brenner 156-369 3,553,053 1/1971 Havens 156-369BENJAMIN A. BORCHELT, Primary Examiner J. V. DORAMUS, Assistant ExaminerUS. Cl. X.R.

